Styrofoam SIS

Styrofoam SIS

Credit: Dow Chemical Co., Building Solutions

What makes this product green?

  • Reduces heating and cooling loads
  • Post-consumer recycled content
  • Prevents moisture or air quality problems


Styrofoam SIS (structural insulated sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. ) provides structural shear bracing, wraparound insulation, and a water-resistant barrier and drainage planePath that water would take over the building envelope. Concealed drainage-plane materials, such as building paper or housewrap, are designed to shed water that penetrates the building’s cladding. Drainage planes are installed to overlap in shingle fashion (weatherlap) so that water flows downward and away from the building envelope. in a single panel. Styrofoam SIS offers its three functions in three layers. A thin structural layer, consisting of up to 80% post-consumer recycled content, rests against the studs. The middle layer is a closed-cell, rigid polyisocyanurate foam with high compressive strength. A blue-colored outer layer composed in part of aluminum foil provides moisture and UV protection and acts as a drainage plane. Additional nails are required to provide holding power, but taping the holes is not necessary. The company does recommend taping the seams with its Weathermate Construction Tape. These panels are available in 4’x8’, 4’x9’, or 4’x10’ dimensions with half-inch and one-inch thicknesses, and provide insulation values of R-3 and R-5.5, respectively.

Manufacturer Information

Dow Chemical Co.
Building Solutions
200 Larkin Ctr.
Midland, MI 48674
Phone: 800-232-2436
Fax: 989-832-1465
Toll-free: 866-583-2583

Listed in: Insulating Sheathing, Moisture-Resistant Sheathing Board